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Abstract:

A vehicular air-conditioning system has a heat pump circulation passage
for circulating a coolant with a compressor. To the heat pump circulation
passage, there are connected a condenser for performing a heat exchange
between a coolant and ambient air, an expansion valve, a first
evaporator, a heater, and a second evaporator. The heat pump circulation
passage includes a coolant retrieval passage extending from a divider
between the condenser and the gas-liquid separator and connected to the
compressor. A second backflow check valve for preventing the coolant from
flowing from the compressor to the divider and a solenoid-operated valve
are connected to the coolant retrieval passage.

Claims:

1. An air-conditioning system for use on a vehicle, comprising: a heat
pump circulation passage for circulating a coolant with a compressor; a
condenser disposed in the heat pump circulation passage, for performing a
heat exchange between the coolant and ambient air; an expansion valve
disposed in the heat pump circulation passage, for depressurizing the
coolant which is delivered from the condenser; a first evaporator
disposed in the heat pump circulation passage, for performing a heat
exchange between the coolant which has passed through the expansion valve
and air-conditioning air; a heater disposed in the heat pump circulation
passage, for performing a heat exchange between the coolant which is
delivered from the compressor and the air-conditioning air which has
passed through the first evaporator; a second evaporator disposed in a
branch passage branched from the heat pump circulation passage, for
performing a heat exchange between the coolant and a heating medium
obtained from within or outside the vehicle; and a gas-liquid separator
and an auxiliary condenser which are disposed downstream of the condenser
and connected between the condenser and the expansion valve; wherein the
heat pump circulation passage includes a coolant retrieval passage
extending from a divider between the condenser and the gas-liquid
separator and connected to the compressor.

2. The air-conditioning system according to claim 1, further comprising
backflow check means connected to the coolant retrieval passage, for
preventing the coolant from flowing from the compressor to the divider.

3. The air-conditioning system according to claim 1, further comprising
an on-off valve connected to the coolant retrieval passage; wherein the
on-off valve is opened in a heating mode and closed in a cooling mode.

4. The air-conditioning system according to claim 2, further comprising
an on-off valve connected to the coolant retrieval passage; wherein the
on-off valve is opened in a heating mode and closed in a cooling mode.

5. The air-conditioning system according to claim 3, further comprising a
controller for switching between the heating mode and the cooling mode
and controlling opening and closing of the on-off valve; wherein in the
heating mode, the controller opens the on-off valve and thereafter
activates the compressor for a prescribed time and then closes the on-off
valve.

6. The air-conditioning system according to claim 4, further comprising a
controller for switching between the heating mode and the cooling mode
and controlling opening and closing of the on-off valve; wherein in the
heating mode, the controller opens the on-off valve and thereafter
activates the compressor for a prescribed time and then closes the on-off
valve.

7. The air-conditioning system according to claim 1, wherein the heating
medium which is supplied to the second evaporator for a heat exchange
with the coolant comprises a medium which is higher in temperature than
the coolant.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2010-005117 filed on Jan. 13, 2010,
of which the contents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a heat-pump vehicular
air-conditioning system for use on a vehicle for air-conditioning the
passenger's cabin of the vehicle.

[0004] 2. Description of the Related Art

[0005] Various vehicular air-conditioning systems have been used for use
on various vehicles including engine vehicle powered by an internal
combustion engine, hybrid vehicles powered by an engine and a secondary
battery (or a secondary battery and a fuel cell), electric vehicles, and
fuel cell vehicles, etc.

[0006] One of such vehicular air-conditioning systems is a heat-pump
air-conditioning system. For example, as shown in FIG. 8 of the
accompanying drawings, a cooling and heating system for use on
automobiles as disclosed in Japanese Patent No. 3929606 includes a
compressor 1, an exterior condenser 2, a liquid tank 3, an expansion
valve 4, and an interior evaporator 5 which are connected successively in
the order named by coolant pipes 6.

[0007] The cooling and heating system also includes a bypass pipe 7 for
guiding a coolant discharged from the compressor 1 directly into the
liquid tank 3 in bypassing relation to the exterior condenser 2. A first
solenoid-operated valve 8a is connected to the coolant pipe 6 that is
connected to the inlet of the exterior condenser 2. An interior condenser
2a and a second solenoid-operated valve 8b are connected to the bypass
pipe 7.

[0008] When the cooling and heating system operates in a cooling mode, the
first solenoid-operated valve 8a is opened and the second
solenoid-operated valve 8b is closed to deliver the coolant discharged
from the compressor 1 into the exterior condenser 2. When the cooling and
heating system operates in a heating mode, the first solenoid-operated
valve 8a is closed and the second solenoid-operated valve 8b is opened to
send the coolant discharged from the compressor 1 into the bypass pipe 7.

[0009] The outlet of the exterior condenser 2 is directly connected to the
inlet of the compressor 1 by a coolant retrieval pipe 9 which is
connected to a third solenoid-operated valve 8c. When the heating mode is
selected, the first solenoid-operated valve 8a, the second
solenoid-operated valve 8b, and the third solenoid-operated valve 8c are
controlled to retrieve the coolant which has remained in the exterior
condenser 2 into a heating cycle.

[0010] According to Japanese Patent No. 3929606, a receiver cycle having
the exterior condenser 2 and the liquid tank 3 which serves as a receiver
tank is employed. Therefore, cavitation (evaporation of the liquid
coolant) occurs in the liquid line, tending to cause an insufficient
coolant flow rate with respect to the opening of the expansion valve 4.

[0011] The receiver cycle suffers from a relatively low cooling
capability. If the cooling capability is to be increased, then the amount
of coolant used and the weight of the cooling and heating system are
increased, making the cooling and heating system less suitable for use on
vehicles. Furthermore, the compressor 1 needs an increase in its ability,
which is detrimental to the fuel economy of the vehicle that incorporates
the cooling and heating system.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a vehicular
air-conditioning system which is of a simple and economical structure,
allows a coolant to circulate stably, has an increased heat exchange
efficiency, and is capable of maintaining a good air-conditioning
capability.

[0013] According to the present invention, there is provided an
air-conditioning system for use on a vehicle, comprising a heat pump
circulation passage for circulating a coolant with a compressor, a
condenser disposed in the heat pump circulation passage, for performing a
heat exchange between the coolant and ambient air, an expansion valve
disposed in the heat pump circulation passage, for depressurizing the
coolant which is delivered from the condenser, a first evaporator
disposed in the heat pump circulation passage, for performing a heat
exchange between the coolant which has passed through the expansion valve
and air-conditioning air, a heater disposed in the heat pump circulation
passage, for performing a heat exchange between the coolant which is
delivered from the compressor and the air-conditioning air which has
passed through the first evaporator, and a second evaporator disposed in
a branch passage branched from the heat pump circulation passage, for
performing a heat exchange between the coolant and a heating medium
obtained from within or outside the vehicle.

[0014] The air-conditioning system also includes a gas-liquid separator
and an auxiliary condenser which are disposed downstream of the condenser
and connected between the condenser and the expansion valve, and the heat
pump circulation passage includes a coolant retrieval passage extending
from a divider between the condenser and the gas-liquid separator and
connected to the compressor.

[0015] According to the present invention, the coolant that remains in the
condenser is retrieved to the compressor due to a pressure difference
which is developed in the coolant retrieval passage connected between the
condenser and the gas-liquid separator. Therefore, the coolant that
remains in the condenser is retrieved easily and quickly for effectively
preventing from dropping in performance.

[0016] The auxiliary condenser is disposed downstream of the gas-liquid
separator with the divider being disposed upstream thereof. The auxiliary
condenser functions as an auxiliary cooling unit when the
air-conditioning system operates in a cooling mode and a heating mode.
There is no need for an auxiliary cooling unit to be used exclusively in
the heating mode, for example.

[0017] Accordingly, it is possible for the air-conditioning system to
circulate the coolant stably with a simple and economical arrangement and
to operate with increased heat exchange efficiency for better
air-conditioning capability.

[0018] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying drawings in
which preferred embodiments of the present invention are shown by way of
illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a diagram, partly in block form, of a vehicular
air-conditioning system according to a first embodiment of the present
invention;

[0020]FIG. 2 is a diagram of the vehicular air-conditioning system shown
in FIG. 1 which operates in a heating mode;

[0021] FIG. 3 is a flowchart of an operation sequence of the vehicular
air-conditioning system shown in FIG. 1;

[0022]FIG. 4 is a diagram of the vehicular air-conditioning system shown
in FIG. 1 which operates in a cooling mode;

[0023]FIG. 5 is a diagram, partly in block form, of a vehicular
air-conditioning system according to a second embodiment of the present
invention;

[0024] FIG. 6 is a diagram of the vehicular air-conditioning system shown
in FIG. 5 which operates in a heating mode;

[0025]FIG. 7 is a diagram of the vehicular air-conditioning system shown
in FIG. 5 which operates in a cooling mode; and

[0026] FIG. 8 is a diagram, partly in block form, of a cooling and heating
system for use on automobiles as disclosed in Japanese Patent No.
3929606.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] As shown in FIGS. 1 and 2, a vehicular air-conditioning system 10
according to a first embodiment of the present invention is mounted on an
automobile (vehicle) 12 for air-conditioning a passenger's cabin
(passenger compartment) 14 of the automobile 12.

[0028] The vehicular air-conditioning system 10 includes a heat pump
circulation passage 18 through which a coolant is circulated by a
compressor 16. To the heat pump circulation passage 18, there are
connected a condenser 20 for performing a heat exchange between the
coolant and the ambient air, an expansion valve 22 for depressurizing the
coolant sent from the condenser 20, a first evaporator 24 for performing
a heat exchange between the coolant that has passed through the expansion
valve 22 and air-conditioning air, and a heater 26 for performing a heat
exchange between the coolant which has been delivered from the compressor
16 and the air-conditioning air that has passed through the first
evaporator 24.

[0029] A branch passage 28 is branched from the heat pump circulation
passage 18 and connected to a second evaporator 30 for performing a heat
exchange between the coolant and a heating medium obtained from within or
outside the automobile 12, e.g., a heating medium discharged from the
cabin 14 out of the automobile 12 (a waste heat gas from the cabin 14).

[0030] Since the heating medium supplied to the second evaporator 30 for a
heat exchange is a waste heat gas from the cabin 14, the heat produced in
the cabin 14 is not wasted but effectively utilized. When the vehicular
air-conditioning system 10 starts to operate in a heating mode, the heat
that is supplied to warm the cabin 14 is retrieved and introduced back
into the vehicular air-conditioning system 10. Consequently, the
vehicular air-conditioning system 10 can quickly start to operate.

[0031] A first backflow check valve (backflow check means) 32a, a
gas-liquid separator 34, and an auxiliary condenser (auxiliary cooling
condenser) 36 are successively disposed downstream of the condenser 20
and connected between the condenser 20 and the expansion valve 22. The
first backflow check valve 32a serves to prevent the coolant from flowing
from the gas-liquid separator 34 to the condenser 20. A solenoid-operated
valve (on-off valve) 38a is disposed upstream of the condenser 20. The
heat pump circulation passage 18 includes a first bypass passage 40a
connected to the gas-liquid separator 34 in bypassing relation to the
condenser 20. A solenoid-operated valve (on-off valve) 38b is connected
to the first bypass passage 40a.

[0032] The heat pump circulation passage 18 also includes a coolant
retrieval passage 44 extending from a divider 42 between the condenser 20
and the gas-liquid separator 34 and connected to the compressor 16. To
the coolant retrieval passage 44, there are connected a second backflow
check valve (backflow check means) 32b for preventing the coolant from
flowing from the compressor 16 to the divider 42, and a solenoid-operated
valve (on-off valve) 38c.

[0033] The expansion valve 22 has a means (not shown) for detecting the
temperature of the coolant which is delivered from the first evaporator
24 that cools the air-conditioning air. The expansion valve 22
automatically changes its opening to change the flow rate of the coolant
depending on the detected temperature of the coolant delivered from the
first evaporator 24.

[0034] The heat pump circulation passage 18 has a three-way valve 46a
connected at the junction between a portion of the heat pump circulation
passage 18 which is positioned near and connected to the expansion valve
22 and an inlet end of the branch passage 28, and a three-way valve 46b
connected at the junction between an outlet end of a second bypass
passage 40b which bypasses the first evaporator 24 and the heat pump
circulation passage 18. The second evaporator 30 is disposed in a rear
portion of the automobile 12 (see FIG. 2).

[0035] An air-mixing damper 48 for delivering the air-conditioning air
which has been cooled by the first evaporator 24 into the cabin 14
without flowing through the heater 26 is disposed between the first
evaporator 24 and the heater 26.

[0036] The automobile 12 has an ambient air inlet 50 for introducing
ambient air as air-conditioning air into the cabin 14. The first
evaporator 24 and the heater 26 are disposed successively in the order
named downstream of the ambient air inlet 50. The vehicular
air-conditioning system 10 also includes a controller (ECU) 52 (see FIG.
1) for controlling overall operation of the vehicular air-conditioning
system 10. The controller 52 also functions as a flow passage switching
means for controlling the solenoid-operated valves 38a, 38b, 38c and the
three-way valves 46a, 46b to switch between a heating mode and a cooling
mode of the vehicular air-conditioning system 10.

[0037] Operation of the vehicular air-conditioning system 10 will be
described below with reference to a flowchart shown in FIG. 3.

[0038] First, it is determined whether the heating mode or the cooling
mode of the vehicular air-conditioning system 10 is selected in step S1.
If the heating mode is selected (YES in step S1), then control goes to
step S2 in which the solenoid-operated valve 38a is closed and the
solenoid-operated valves 38b, 38c are opened.

[0039] Then, the compressor 16 is activated in step S3. The compressor 16
now delivers the coolant into the heat pump circulation passage 18. The
coolant is supplied to the heater 26 which performs a heat exchange
between the coolant and the air-conditioning air, i.e., radiates the heat
from the coolant to the air-conditioning air, thereby increasing the
temperature of the air-conditioning air.

[0040] As the solenoid-operated valve 38a is closed and the
solenoid-operated valve 38b is open, the coolant discharged from the
heater 26 flows through the first bypass passage 40a into the gas-liquid
separator 34 in bypassing relation to the condenser 20. The coolant is
cooled while it flows through the gas-liquid separator 34 and the
auxiliary condenser 36, and then is sent to the expansion valve 22.

[0041] The coolant is depressurized by the expansion valve 22 and flows
through the three-way valve 46a into the branch passage 28, from which
the coolant is introduced into the second evaporator 30. The second
evaporator 30 performs a heat exchange between the coolant and the heat
from the cabin 14. The coolant then flows from the second evaporator 30
and through the second bypass passage 40b and the expansion valve 22 in
bypassing relation to the first evaporator 24, and is then delivered
again to the compressor 16.

[0042] According to the first embodiment, the coolant retrieval passage 44
extends from the divider 42 between the condenser 20 and the gas-liquid
separator 34 and is connected to the compressor 16, and the
solenoid-operated valve 38c connected to the coolant retrieval passage 44
is open at this time.

[0043] When the compressor 16 is actuated while in the heating mode, a
pressure difference is developed in the coolant retrieval passage 44.
Specifically, in the coolant retrieval passage 44, the pressure at the
compressor 16 is lower than the pressure at the divider 42. Therefore,
the coolant in the form of a liquid which remains in the condenser 20 is
forcibly drawn, i.e., retrieved, toward the compressor 16 through the
coolant retrieval passage 44 due to the pressure difference in the
coolant retrieval passage 44. Accordingly, the coolant in the form of a
liquid which remains in the condenser 20 is easily and quickly retrieved,
and the condenser 20 is prevented from dropping in performance.

[0044] In the heating mode, the heater 26 is connected downstream directly
to the gas-liquid separator 34 in bypassing relation to the condenser 20.
Therefore, the gas-liquid separator 34 functions as an auxiliary cooling
tank, and the auxiliary condenser 36 functions as an auxiliary cooling
unit.

[0045] The coolant is thus introduced as a fully liquid medium into the
expansion valve 22, with any gas being prevented from being trapped
therein. The coolant is thus stably circulated in the heat pump
circulation passage 18 for higher heat exchange efficiency.

[0046] Since the gas-liquid separator 34 functions as an auxiliary cooling
tank, a sufficient amount of coolant is maintained in the vehicular
air-conditioning system 10. Consequently, the vehicular air-conditioning
system 10 is prevented from dropping in air-conditioning performance due
to a shortage of coolant while the vehicular air-conditioning system 10
is operating in a transient period.

[0047] In the first embodiment, there is no need for an auxiliary cooling
tank and an auxiliary cooling unit to be used exclusively in the heating
mode because the gas-liquid separator 34 and the auxiliary condenser 36
can be used also in the cooling mode. Accordingly, it is possible for the
vehicular air-conditioning system 10 to circulate the coolant stably with
a simple and economical arrangement and to operate with increased heat
exchange efficiency for better air-conditioning capability.

[0048] If the compressor 16 has been actuated for a given time (prescribed
time) (YES in step S4), then control goes to step S5 in which the
solenoid-operated valve 38c is closed. Thus, the coolant stops being
retrieved from the condenser 20, and the vehicular air-conditioning
system 10 enters a normal heating mode. If it is judged that the heating
mode is stopped (YES in step S6), then the vehicular air-conditioning
system 10 is shut down.

[0049] If the heating mode is not selected (NO in step S1), then control
goes to step S7 which determines whether the cooling mode of the
vehicular air-conditioning system 10 is selected or not. If it is judged
that the cooling mode is not selected (NO in step S7), then control jumps
to step S6. If it is judged that the cooling mode is selected (YES in
step S7), then control goes to step S8.

[0050] In step S8, the solenoid-operated valve 38a is opened and the
solenoid-operated valves 38b, 38c are closed. Then, control goes to step
S9 in which the compressor 16 is activated. The vehicular
air-conditioning system 10 now starts to operate in the cooling mode, as
shown in FIG. 4.

[0051] In the cooling mode, the solenoid-operated valve 38a is opened to
connect the condenser 20 to the heat pump circulation passage 18. The
three-way valves 46a, 46b are switched to disconnect the branch passage
28 from the heat pump circulation passage 18 and connect the first
evaporator 24 to the heat pump circulation passage 18. The air-mixing
damper 48 is brought into a fully closed position, i.e., a position to
cover the heater 26.

[0052] The coolant which has been compressed and heated to a higher
temperature by the compressor 16 flows through the heater 26 and is
cooled by the condenser 20, the gas-liquid separator 34, and the
auxiliary condenser 36. The coolant becomes lower in temperature and
pressure in the expansion valve 22, and then is supplied to the first
evaporator 24. The first evaporator 24 performs a heat exchange between
the coolant which is lower in temperature and pressure and the
air-conditioning air, thereby cooling the air-conditioning air. After
having absorbed the heat from the air-conditioning air, the coolant is
returned from the expansion valve 22 to the compressor 16.

[0053] Inasmuch as the air-mixing damper 48 is closed, the
air-conditioning air cooled by the first evaporator 24 is not heated by
the heater 26, and is introduced into the cabin 14, cooling the cabin 14.
In the cooling mode, the gas-liquid separator 34 provides a damping
action on the coolant as it increases or decreases in volume.

[0054]FIG. 5 is a diagram, partly in block form, of a vehicular
air-conditioning system 60 according to a second embodiment of the
present invention. Those parts of the vehicular air-conditioning system
60 which are identical to those of the vehicular air-conditioning system
10 according to the first embodiment are denoted by identical reference
characters, and will not be described in detail below.

[0055] The vehicular air-conditioning system 60 is mounted on an
automobile (vehicle) 62 (see FIG. 6). As shown in FIGS. 5 and 6, the heat
pump circulation passage 18 includes a condenser unit 64 as an auxiliary
cooling condenser, which provides an auxiliary cooling cycle. The
condenser unit 64 is disposed downstream of the heater 26 and is
connected in series thereto. The condenser unit 64 comprises a main
condenser (condensing unit) 20a, a gas-liquid separating coolant storage
(auxiliary cooling tank) 34a, and an auxiliary condenser (supercooling
unit) 36a, through which the coolant flows in the cooling mode.

[0056] The heat pump circulation passage 18 includes a coolant retrieval
passage 44a extending from a divider 42a at an end of the main condenser
20a and connected to the compressor 16. The second backflow check valve
32b and the solenoid-operated valve 38c are connected to the coolant
retrieval passage 44a.

[0057] According to the second embodiment, the vehicular air-conditioning
system 60 operates in the heating mode and the cooling mode according to
the flowchart shown in FIG. 3, as with the vehicular air-conditioning
system 10 according to the first embodiment.

[0058] When the vehicular air-conditioning system 60 operates in the
heating mode, as shown in FIG. 6, the solenoid-operated valve 38a is
closed and the solenoid-operated valves 38b, 38c are opened. In the
heating mode, the coolant in the form of a liquid which remains in the
condenser 20 is forcibly drawn toward the compressor 16 due to the
pressure difference in the coolant retrieval passage 44a. Consequently,
the vehicular air-conditioning system 60 according to the second
embodiment offers the same advantages as the vehicular air-conditioning
system 10 according to the first embodiment, e.g., it allows the coolant
in the form of a liquid to be well and reliably retrieved.

[0059] When the vehicular air-conditioning system 60 operates in the
cooling mode, as shown in FIG. 7, the solenoid-operated valve 38a is
opened and the solenoid-operated valves 38b, 38c are closed. Therefore,
the vehicular air-conditioning system 60 according to the second
embodiment offers the same advantages as the vehicular air-conditioning
system 10 according to the first embodiment.

[0060] In each of the first and second embodiments, the heating medium
supplied to the second evaporator 30 for a heat exchange may be any
medium which is higher in temperature than the coolant that flows into
the second evaporator 30, e.g., a medium heated by motors, a medium
heated by batteries, a medium heated by an internal combustion engine if
the automobile 12 or 62 is powered by such an internal combustion engine,
a medium heated by the controller 52, a medium carrying ambient heat, or
the like, in addition to the waste heat gas from the cabin 14.

[0061] Each of the three-way valves 46a, 46b may comprise an integral
structure including a three-way dividing mechanism and a valve mechanism
or a combination of a dividing block and a solenoid-operated valve.

[0062] Although certain preferred embodiments of the present invention
have been shown and described in detail, it should be understood that
various changes and modifications may be made therein without departing
from the scope of the appended claims.